Sub ReadDataFromCloseFile()

    On Error GoTo ErrHandler
    Application.ScreenUpdating = False

    Dim workbookArr() As Workbook
    Dim totalRows() As Integer
    Dim existedCount As Long
    Dim fileIndex As Long

    'SHOW USERFORM
    ui.Show

    ' OPEN THE SOURCE EXCEL WORKBOOK IN "READ ONLY MODE".
    existedCount = ui.ListBox1.ListCount
    ReDim workbookArr(existedCount)

    Set workbookArr(0) = Workbooks.Open(ui.TextBox1.Text, True, False)
    For fileIndex = 1 To existedCount
        Set workbookArr(fileIndex) = Workbooks.Open(ui.ListBox1.List(fileIndex - 1), True, False)
    Next fileIndex

    '==================================================================

    ' GET THE TOTAL ROWS FROM THE SOURCE WORKBOOK.
    ReDim totalRows(existedCount)

    For i = 0 To existedCount
        totalRows(i) = workbookArr(i).Worksheets("Sheet1").Range("A1048576").End(xlUp).Row
    Next i

    ' GIVE EACH ROW UNIQUE ID
    Dim myConcatenateCell As String
    myConcatenateCell = "AA" & "2" 'TODO: VISUALLY WE CHOOSE THIS CELL TO APPLY, NEED TO AUTO FIND IT LATER

    For i = 0 To existedCount
        workbookArr(i).Worksheets("Sheet1").Range(myConcatenateCell & ":AA" & CStr(totalRows(i) + 1)).FormulaR1C1 = "=CONCATENATE(RC[-21],RC[-18])"
    Next i

    ' CLASSIFY EACH TRANSACTION HERE. RETURN 1 IF EXISTED, 0 IF NOT
    Dim myFirstColumn As Long
    Dim myLastColumn As Long
    Dim myColumnIndex As Long
    Dim myFirstRow As Long
    Dim myLastRow As Long
    Dim myVLookupResult As Variant
    Dim myTableArray As Range
    Dim lookUpValue As String

    myFirstColumn = 27 'TODO: FIND SUITABLE COLUMN
    myLastColumn = 27
    myColumnIndex = 1
    myFirstRow = 2
    myLastRow = totalRows(1)

    With workbookArr(1).Worksheets("Sheet1")
        Set myTableArray = .Range(.Cells(myFirstRow, myFirstColumn), .Cells(myLastRow, myLastColumn))
    End With

    ' ITERATE EVERY EXISTED FILE
    For i = 1 To existedCount
        With workbookArr(i).Worksheets("Sheet1")
            Set myTableArray = .Range(.Cells(myFirstRow, myFirstColumn), .Cells(myLastRow, myLastColumn))
        End With

        For j = 2 To totalRows(0)
            lookUpValue = workbookArr(0).Worksheets("Sheet1").Range("AA" & CStr(j)).Value
            myVLookupResult = Application.VLookup(lookUpValue, myTableArray, myColumnIndex, False)
            If (IsError(myVLookupResult)) Then
                workbookArr(0).Worksheets("Sheet1").Range("AB" & CStr(j)).Value = 0
            Else: workbookArr(0).Worksheets("Sheet1").Range("AB" & CStr(j)).Value = 1
            End If
        Next j
    Next i

    ' TODO: DELETE CODE COLUMN

    '==================================================================

    ' CLOSE THE SOURCE FILE.
    workbookArr(0).Close True             ' TRUE - SAVE THE SOURCE FILE.
    Set srcNew = Nothing

    workbookArr(1).Close False             ' FALSE - DON'T SAVE THE SOURCE FILE.
    Set srcOld1 = Nothing

    workbookArr(2).Close False             ' FALSE - DON'T SAVE THE SOURCE FILE.
    Set srcOld2 = Nothing

ErrHandler:
    Application.EnableEvents = True
    Application.ScreenUpdating = True

End Sub